The present invention relates to computer-based fault tolerant information systems.
Information systems are finding increased use in applications for which uninterrupted access to reliable data bases is important. For example, one type of computer-based information system common in large companies is the management information system, or MIS. A management information system is a computerized system used by the company's management and personnel to handle purchase and shipping orders and to perform tasks related to accounts payable and receivable, payroll, personnel management, word processing, and other business, managerial and clerical work.
An important goal for management information systems, as well as other information systems, is fault tolerance. When for example an MIS goes down due to a fault, purchase orders from customers cannot be taken and other tasks are suspended, resulting in large financial losses.
Thus, it is desirable to provide an information system that is not brought down by a fault but that stays on line and, moreover, continues to provide correct information. This is particularly important for multinational corporations with offices scattered across different time zones. While some offices are closed, offices in other time zones are open, and the MIS may have to be on line 24 hours a day, 7 days a week to support worldwide operation of such a corporation.